Polarizer and liquid crystal display including the same

ABSTRACT

A polarizer includes a first laminated structure having a first layer with a first refractive index and a second layer with a second refractive index, wherein the first and second refractive indices are different from each other. A buffer layer is disposed on the first laminated structure. A second laminated structure in the polarizer has a third layer with a third refractive index and a fourth layer with a fourth refractive index, wherein the third and fourth refractive indices are different from each other.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. application Ser. No.13/846,018, filed on Mar. 18, 2013, and claims priority from and thebenefit of Korean Patent Application No. 10-2012-0131714, filed on Nov.20, 2012, which are incorporated by reference for all purposes as if setforth herein.

BACKGROUND

Field

Exemplary embodiments relate to display technology, and moreparticularly, to reflective polarizers and liquid crystal displaysincluding the same.

Discussion

A liquid crystal display, which is one of the most common types of flatpanel displays, typically includes two panels with field generatingelectrodes disposed thereon, such as a pixel electrode, a commonelectrode, and the like, and a liquid crystal layer disposedtherebetween. The liquid crystal display is configured to apply anelectric field in the liquid crystal layer by applying voltage to thefield generating electrodes, and determine the direction of liquidcrystal molecules of the liquid crystal layer by the generated electricfield, and control polarization of incident light to faciliate thedisplay of images.

Conventional liquid crystal displays are typically classified into threecategories, e.g., transmissive liquid crystal displays, reflectiveliquid crystal displays, and transflective liquid crystal displays. Atransmissive liquid crystal display may be configured to display animage by using a backlight positioned at a rear side of a liquid crystalcell. A reflective liquid crystal display may be configured to displayan image by using external natural light. A transflective liquid crystaldisplay may be configured to operate in a transmissive mode to displayan image by using an embedded light source of a display element whileindoors or in a dark place where external light is limited and operatein a reflective mode to display an image by reflecting external light inan outdoor high-illumination environment. In this manner, atransflective liquid crystal display may combine structures of theabove-noted transmissive liquid crystal display and the reflectiveliquid crystal display.

Among liquid crystal displays, the transmissive or transflective liquidcrystal displays that are configured to display images by using abacklight are mainly used because their display luminance is relativelyhigher than traditionally reflective liquid crystal displays.

It is noted, however, that about 50% of light radiating from a backlightand made incident on a polarizer is absorbed by the polarizer, which istypically coupled to a lower portion of a corresponding liquid crystaldisplay. As such, the remaining about 50% of light may be used fordisplaying an image. As a result, light efficiency and display luminancemay be less than acceptable.

Therefore, there is a need for an approach that provides efficient, costeffective techniques to provide liquid crystal display devices withimproved light efficiency and display luminance.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention, andtherefore, it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

SUMMARY

Exemplary embodiments provide polarizers and liquid crystal displaysincluding the same configured to increase light efficiency supplied froma backlight unit, and thereby, also increase display luminance.

Additional aspects will be set forth in the detailed description whichfollows and, in part, will be apparent from the disclosure, or may belearned by practice of the invention.

According to exemplary embodiments, a polarizer includes a firstlaminated structure having a first layer with a first refractive indexand a second layer with a second refractive index, wherein the first andsecond refractive indices are different from each other. A buffer layeris disposed on the first laminated structure. A second laminatedstructure in the polarizer has a third layer with a third refractiveindex and a fourth layer with a fourth refractive index, wherein thethird and fourth refractive indices are different from each other.

According to exemplary embodiments, a liquid crystal display includes afirst panel having a first polarizer configured as an absorptivepolarizer, and a first insulation substrate; a second panel having asecond polarizer, and a second insulation substrate; a liquid crystallayer disposed between the first panel and the second panel; and abacklight providing unit configured to supply light. The second panel isdisposed on the backlight providing unit. The second polarizer includesa first laminated structure having a first layer with a first refractiveindex and a second layer with a second refractive index, wherein thefirst and second refractive indices are different from each other. Thesecond polarizer further includes a buffer layer disposed on the firstlaminated structure, and a second laminated structure comprising a thirdlayer having a third refractive index and a fourth layer having a fourthrefractive index. The third and fourth refractive indices are differentfrom each other.

The foregoing general description and the following detailed descriptionare exemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of theinvention, and together with the description serve to explain theprinciples of the invention.

FIG. 1 is a cross-sectional view of a liquid crystal display, accordingto exemplary embodiments.

FIG. 2 is a cross-sectional view of a reflective polarizer, according toexemplary embodiments.

FIG. 3 is a cross-sectional view of a main body of a reflectivepolarizer, according to exemplary embodiments.

FIG. 4 is a cross-sectional view of an absorptive polarizer, accordingto exemplary embodiments.

FIG. 5 is a diagram comparing viewing angle characteristics of a liquidcrystal display, according to exemplary embodiments.

FIGS. 6 and 7 are cross-sectional views of a reflective polarizer and aliquid crystal layer, according to exemplary embodiments.

FIG. 8 is a cross-sectional view of a reflective polarizer, according toexemplary embodiments.

FIGS. 9-12 are diagrams of display characteristics of a liquid crystaldisplay, according to exemplary embodiments.

FIGS. 13 and 14 are diagrams of display characteristics of a liquidcrystal display, according to exemplary embodiments.

FIG. 15 is a diagram of a manufacturing method of the reflectivepolarizer of FIG. 8, according to exemplary embodiments.

FIG. 16 is a cross-sectional view of a reflective polarizer, accordingto exemplary embodiments.

FIG. 17 is a cross-sectional view of a liquid crystal display, accordingto exemplary embodiments.

FIG. 18 is a diagram of display characteristics of the liquid crystaldisplay of FIG. 17, according to exemplary embodiments.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of various exemplary embodiments. It is apparent, however,that various exemplary embodiments may be practiced without thesespecific details or with one or more equivalent arrangements. In otherinstances, well-known structures and devices are shown in block diagramform in order to avoid unnecessarily obscuring various exemplaryembodiments.

In the accompanying figures, the size and relative sizes of layers,films, panels, regions, etc., may be exaggerated for clarity anddescriptive purposes. Also, like reference numerals denote likeelements.

When an element or layer is referred to as being “on,” “connected to,”or “coupled to” another element or layer, it may be directly on,connected to, or directly coupled to the other element or layer orintervening elements or layers may be present. When, however, an elementor layer is referred to as being “directly on,” “directly connected to,”or “directly coupled to” another element or layer, there are nointervening elements or layers present. For the purposes of thisdisclosure, “at least one of X, Y, and Z” and “at least one selectedfrom the group consisting of X, Y, and Z” may be construed as X only, Yonly, Z only, or any combination of two or more of X, Y, and Z, such as,for instance, XYZ, XYY, YZ, and ZZ. Like numbers refer to like elementsthroughout. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items.

Although the terms first, second, etc. may be used herein to describevarious elements, components, regions, layers and/or sections, theseelements, components, regions, layers and/or sections should not belimited by these terms. These terms are only used to distinguish oneelement, component, region, layer or section from another region, layeror section. Thus, a first element, component, region, layer or sectiondiscussed below could be termed a second element, component, region,layer or section without departing from the teachings of the presentdisclosure.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper,” and/or the like, may be used herein for descriptive purposesand, thereby, to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the drawings.Spatially relative terms are intended to encompass differentorientations of an apparatus in use or operation in addition to theorientation depicted in the drawings. For example, if the apparatus inthe drawings is turned over, elements described as “below” or “beneath”other elements or features would then be oriented “above” the otherelements or features. Thus, the exemplary term “below” can encompassboth an orientation of above and below. Furthermore, the apparatus maybe otherwise oriented (e.g., rotated 90 degrees or at otherorientations) and, as such, the spatially relative descriptors usedherein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting. As used herein, thesingular forms, “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. Moreover,the terms “comprises” and/or “comprising,” when used in thisspecification, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Various exemplary embodiments are described herein with reference tosectional illustrations that are schematic illustrations of idealizedexemplary embodiments and/or intermediate structures. As such,variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, exemplary embodiments disclosed herein should not beconstrued as limited to the particular illustrated shapes of regions,but are to include deviations in shapes that result from, for instance,manufacturing. For example, an implanted region illustrated as arectangle will, typically, have rounded or curved features and/or agradient of implant concentration at its edges rather than a binarychange from implanted to non-implanted region. Likewise, a buried regionformed by implantation may result in some implantation in the regionbetween the buried region and the surface through which the implantationtakes place. Thus, the regions illustrated in the drawings are schematicin nature and their shapes are not intended to illustrate the actualshape of a region of a device and are not intended to be limiting.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure is a part. Terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and will not be interpreted in anidealized or overly formal sense, unless expressly so defined herein.

While exemplary embodiments are described in association with a liquidcrystal display device, it is contemplated that exemplary embodimentsmay be utilized in association with other or equivalent display devices,such as various self-emissive and/or non-self-emissive displaytechnologies. For instance, self-emissive display devices may includeorganic light emitting displays (OLED), plasma display panels (PDP),etc., whereas non-self-emissive display devices may constitute liquidcrystal displays (LCD), electrophoretic displays (EPD), electrowettingdisplays (EWD), and/or the like.

FIG. 1 is a cross-sectional view of a liquid crystal display, accordingto exemplary embodiments. FIG. 2 is a cross-sectional view of areflective polarizer, according to exemplary embodiments. FIG. 3 is across-sectional view of a main body of a reflective polarizer, accordingto exemplary embodiments. FIG. 4 is a cross-sectional view of anabsorptive polarizer, according to exemplary embodiments.

According to exemplary embodiments, the liquid crystal display includesbacklight unit 500, optical sheet 25, liquid crystal layer 3, lowerpanel 100, and upper panel 200.

While not illustrated, backlight unit 500 includes a light source, alight guide plate, and a reflector. Optical sheet 25 is disposed onbacklight unit 500.

The configuration of backlight unit 500 enables light supplied from thelight source to pass through the light guide plate and the reflector,and thereby, to be discharged upward from the backlight unit 500 andpass through the optical sheet 25 disposed on backlight unit 500. Inthis manner, the light may propagate through lower panel 100, liquidcrystal layer 3, and upper panel 200.

According to exemplary embodiments, the light source may be (orotherwise include), for example, a fluorescent lamp (such as acold-cathode fluorescent lamp (CCFL)), a light emitting diode (LED),and/or the like. The light source may be disposed on a side or a lowersurface of the backlight unit 500.

The optical sheet 25 may include at least one optical sheet and mayinclude a prism sheet including a prism structure or a diffusion film,such as a diffuser. In exemplary embodiments, the optical sheet 25 maynot include a luminance improvement film that typically includes twolayers having different refractive indices that are repetitively formed.Namely, because a lower polarizer 12 may be utilized that includes arepetitively laminated structure 12-11 that includes a multilayer (e.g.,two layer) structure having different refractive indices repetitivelyformed, improved characteristics in luminance may be achieved withoutthe use of a luminance improvement film associated with optical sheet25.

As seen in FIG. 1, lower panel 100, liquid crystal layer 3, and upperpanel 200 may be disposed on the backlight unit 500 and the opticalsheet 25.

First, the lower panel 100 will be described.

According to exemplary embodiments, lower panel 100 may include a lowerpolarizer 12 and a lower insulation substrate 110. The lower polarizer12 is coupled to the lower insulation substrate 110, which may be madeof (or include) transparent glass or plastic.

The lower polarizer 12 may be a reflective polarizer, and may include areflective polarizer main body 12-1 that includes a multilayer structure(e.g., two layers) having different refractive indices that arerepetitively formed, and an Rth phase compensation layer 12-2.

The reflective polarizer main body 12-1 may include at least onerepetitively laminated structure 12-11 in which, for example, two layershaving different refractive indices are repetitively formed. As seen inFIG. 3, the reflective polarizer main body 12-1 may include, forinstance, three repetitively laminated structures 12-11. It iscontemplated; however, that repetitively laminated structure 12-11 mayinclude any suitable number of repetitively formed layers, andreflective polarizer main body 12-1 may include any suitable number ofthe repetitively laminated structures 12-11.

According to exemplary embodiments, the repetitively laminated structure12-11 may be a structure formed by repetitively laminating a firstrefractive index layer (e.g., polymer A) and a second refractive indexlayer (e.g., polymer B) upon one another. The number of total layers maybe any suitable number, but in exemplary embodiments, the repetitivelylaminated structure 12-11 may be formed with, for instance, a total of275 layers. Again, any suitable number of total layers may be utilized.

In exemplary embodiments, such as illustrated in FIG. 3, a thickness ofthe first refractive index layer (e.g., polymer A) may be smaller than athickness of the second refractive index layer (e.g., polymer B).Further, the first refractive index layer may include a higherrefractive index than the second refractive index layer. However,depending on the choice of materials utilized, the thickness of thefirst refractive index layer may be larger than the thickness of thesecond refractive index layer, the thicknesses may be the same as eachother, and/or the first refractive index layer may have a smallerrefractive index than the second refractive index layer. According toexemplary embodiments, each of the two layers used in the repetitivelylaminated structure 12-11 may have a different refractive index, and mayhave a difference in only a refractive index in one axial directionamong three axial directions.

The reflective polarizer main body 12-1 may also include a buffer layer12-5 disposed between repetitively laminated structures 12-11 and/ordisposed on one or more of the outermost surfaces of the uppermost andlowermost repetitively laminated structures 12-11. The buffer layer 12-5may be formed with one of the various layers (e.g., polymer B having alow refractive index) included in the repetitively laminated structure12-11. The buffer layer 12-5 may be configured to protect, support,and/or connect the repetitively laminated structures 12-11.

According to exemplary embodiments, the Rth phase compensation layer12-2 uses a triacetyl-cellulose (TAC) layer to compensate for a phase inan Rth direction. Since the TAC layer may have a retardation value ofthe Rth direction according to a thickness of the layer, when a phasevalue of the Rth direction to be compensated is determined, the TAClayer may be formed to a thickness depending on the determined phasevalue of the Rth phase compensation layer 12-2. In the case of formingthe TAC layer to a thickness of 40 μm, the retardation value of the Rthdirection may be provided as 40 nm. In the case of forming the TAC layerto a thickness of 60 μm, the retardation value of the Rth direction maybe provided as 46 nm. It is contemplated, however, that the numericalvalues may be changed depending on a characteristic of the particularTAC layer being utilized, and in the case of using the TAC layer, as thethickness increases, the provided retardation value of the Rth directionincreases.

According to exemplary embodiments, the lower polarizer 12 is coupled tothe outer side of the lower insulation substrate 110, and includes anadhesive 12-3 for attachment. In FIG. 2, since only the layer providingthe phase retardation is illustrated, the lower insulation substrate 110is omitted.

Although not illustrated, a thin film transistor and a pixel electrodemay be formed on an inner side of the lower insulation substrate 110.The thin film transistor and the pixel electrode may be formed in anyone of various structures. An alignment layer (not shown) may bedisposed on the pixel electrode.

Hereinafter, the upper panel 200 will be described.

According to exemplary embodiments, an upper polarizer 22 may bedisposed on an upper insulation substrate 210 made of, for instance,transparent glass or plastic.

The upper polarizer 22 may include a structure as illustrated in FIG. 4and may be an absorptive polarizer. That is, the upper polarizer 22,which is an absorptive polarizer, may include a TAC layer 22-2 isdisposed on the upper surface of a polyvinyl alcohol (PVA) layer 22-1,and a biaxial compensation layer 22-3 may be disposed on the lowersurface of the PVA layer 22-1. The biaxial compensation layer 22-3 isconfigured to provide phase retardation to improve display quality.

According to exemplary embodiments, the upper polarizer 22 may becoupled to an outer side of the upper insulation substrate 210. An outersurface of the TAC layer 22-2 of the upper polarizer 22 may be subjectedto one or more surface treatments, such as one or more anti-glare oranti-reflection treatments.

While not illustrated, a light blocking member, a color filter, and acommon electrode may be disposed on (or formed inside) the upperinsulation substrate 210. According to exemplary embodiments, the lightblocking member or the color filter may be formed inside the lowerinsulation substrate 110. An alignment layer (not shown) may be disposedbelow the common electrode.

A liquid crystal layer 3 may be disposed between the upper panel 200 andthe lower panel 100.

The liquid crystal layer 3 may include liquid crystal molecules havingpositive dielectric anisotropy. That is, long axes of the liquid crystalmolecules may be horizontal to the surfaces of lower and upper panels100 and 200 when an electric field is not applied to the liquid crystallayer 3. To this end, when an electric field is applied by, forinstance, the pixel electrode and the common electrode, an alignmentdirection of the liquid crystal molecules may be changed in a verticaldirection, e.g., perpendicular or substantially perpendicular to thesurfaces of the lower and upper panels 100 and 200. The liquid crystallayer 3 may use a twisted nematic (TN) mode liquid crystal.

As described above, the liquid crystal display uses a reflectivepolarizer having a phase compensation characteristic of an Rth directionas the lower polarizer 12. Generally, in the case of using a reflectivepolarizer without the phase compensation characteristic of an Rthdirection, a viewing angle is decreased, but in the case of using thereflective polarizer having the phase compensation characteristic of theRth direction, the viewing angle is not decreased. Here, the viewingangle is an angle at a position where a CR ratio is 10:1. Theaforementioned maintenance of a suitably wide viewing angle wassubstantiated in an experiment, the results of which are shown in FIG.5.

FIG. 5 is a diagram comparing viewing angle characteristics of a liquidcrystal display, according to exemplary embodiments.

In FIG. 5, a reflective POL(polarizer) sample 1 and a reflectivePOL(polarizer) sample 2 are simulation results of a liquid crystaldisplay using a reflective polarizer without the phase compensationcharacteristic of the Rth direction, and a reflective POL+TAC (40 μm)and a reflective POL+TAC (60 μm) are simulation results of a liquidcrystal display that compensates for a phase of the Rth direction by thecorresponding numerical value using the TAC layer as illustrated in FIG.1.

As illustrated in FIG. 5, a viewing angle is not changed in a verticaldirection, but in terms of compensating for the phase in the Rthdirection, the viewing angle is increased by 3 to 5 degrees in ahorizontal direction. As a result, the viewing angle of the TN modeliquid crystal layer 3 is increased so as to have a phase compensationcharacteristic of the Rth direction while using the reflectivepolarizer.

In FIG. 2, a TAC layer is utilized as the layer for compensating for thephase of the Rth direction.

However, another layer, in addition to the TAC layer, may be used as thelayer for compensating for the phase of the Rth direction, which isshown and will be described in association with FIGS. 6 and 7.

FIGS. 6 and 7 are cross-sectional views of a reflective polarizer and aliquid crystal layer, according to exemplary embodiments.

First, FIG. 6 illustrates utilization of a negative C plate as an Rthphase compensation layer 12-2′, as opposed to the Rth phase compensationlayer 12-2 shown in FIG. 2. According to exemplary embodiments, thenegative C plate may correspond to an optical anisotropic film having anegative birefringence in its axial direction, i.e., in its thicknessdirection. Since the negative C plate may be configured to compensatefor a phase of the Rth direction, there is an advantage in that theviewing angle is enlarged in the TN mode liquid crystal display utilizedin association with the above-noted experiment, the results of which areshown in FIG. 5.

FIG. 7 illustrates the lower polarizer 12 without the Rth phasecompensation layers 12-2 or 12-2′, unlike as shown in association withFIGS. 2 and 6. As seen in FIG. 7, the Rth phase compensation layer 12-2is not separately added, and an internal Rth phase compensation layer12-2″ configured to compensate for the phase of the Rth direction isformed in the reflective polarizer main body 12-1.

The reflective polarizer main body 12-1 of FIG. 7 will be describedbelow.

The reflective polarizer main body 12-1 of FIG. 7 includes threerepetitively laminated structures 12-11, in which, for instance, twolayers having different refractive indices are repetitively formed uponone another. So long as the number of repetitively laminated structures12-11 is one or more, it is sufficient, and the number may be differentaccording to exemplary embodiments. A buffer layer 12-5 may be disposedbetween the repetitively laminated structures 12-11 and below therepetitively laminated structures 12-11. The buffer layer 12-5 may beformed by one of the various layers included in the repetitivelylaminated structure 12-11, such as polymer B having a lower refractiveindex. The buffer layer 12-5 may be configured to protect or connect therepetitively laminated structures 12-11.

Meanwhile, the internal Rth phase compensation layer 12-2″ is formedabove, for instance, the uppermost repetitively laminated structure12-11; that is, disposed closest to the liquid crystal layer 3. Theinternal Rth phase compensation layer 12-2″ may be formed by a TAC, anegative C plate, or a cyclo olefin polymer (COP).

According to exemplary embodiments, a buffer layer 12-5 may be addedbetween the internal Rth phase compensation layer 12-2″ and theuppermost repetitively laminated structure 12-11.

An adhesive 12-3 is disposed above the internal Rth phase compensationlayer 12-2″ to enable coupling to the lower insulation substrate 110.

In the lower polarizer 12, the reflective polarizer main body 12-1includes the Rth phase compensation layer 12-2″, the buffer layer 12-5is disposed at the lower outer side of three repetitively laminatedstructures 12-11, and the Rth phase compensation layer 12-2″ is disposedat the upper outer side.

In FIGS. 6 and 7, a structure between the lower polarizer 12 and theliquid crystal layer 3 is omitted because constituent elements supplyinga phase difference to light are illustrated. However, it is noted thatone or more constituent elements may be disposed on or among the variousillustrated constituent elements.

According to exemplary embodiments, various additions and/oralternations may be utilized, such as will be described with referenceto FIGS. 8-20.

It is generally noted that associated liquid crystal displays associatedwith FIGS. 8-20 have structures similar to the structure described inassociation with FIG. 1. Namely, liquid crystal displays associated withFIGS. 8-20 may include backlight unit 500, optical sheet 25, lower panel100, liquid crystal layer 3, and upper panel 200.

While not illustrated, backlight unit 500 includes a light source, alight guide plate, and a reflector. Optical sheet 25 is disposed onbacklight unit 500.

The configuration of backlight unit 500 enables light supplied from thelight source to pass through the light guide plate and the reflector,and thereby, to be discharged upward from the backlight unit 500 andpass through the optical sheet 25 disposed on backlight unit 500. Inthis manner, the light may propagate through lower panel 100, liquidcrystal layer 3, and upper panel 200.

According to exemplary embodiments, the light source may be (orotherwise include), for example, a fluorescent lamp (such as a CCFL), aLED, and/or the like. The light source may be disposed on a side or alower surface of the backlight unit 500.

The optical sheet 25 may include at least one optical sheet and mayinclude a prism sheet including a prism structure or a diffusion film,such as a diffuser. In exemplary embodiments, the optical sheet 25 maynot include a luminance improvement film that typically includes twolayers having different refractive indices that are repetitively formed.Namely, because a lower polarizer 12 may be included that includes arepetitively laminated structure 12-11 that includes a multilayer (e.g.,two layer) structure having different refractive indices repetitivelyformed, improved characteristics in luminance may be achieved withoutthe use of a luminance improvement film associated with optical sheet25.

Lower panel 100, liquid crystal layer 3, and upper panel 200 may bedisposed on the backlight unit 500 and the optical sheet 25.

First, the lower panel 100 will be described.

According to exemplary embodiments, lower panel 100 may include a lowerpolarizer 12 and a lower insulation substrate 110. The lower polarizer12 is coupled to the lower insulation substrate 110, which may be madeof (or include) transparent glass or plastic.

The lower polarizer 12 may be a reflective polarizer, and may include atleast two repetitively laminated structures 12-11 and 12-12, in which,for example, two layers having different refractive indices arerepetitively formed. Hereinafter, the repetitively laminated structureswill be referred to as a first repetitively laminated structure 12-11and a second repetitively laminated structure 12-12. In the firstrepetitively laminated structure 12-11 and the second repetitivelylaminated structure 12-12, two layers having different refractiveindices may be repetitively formed upon one another, but the higherrefractive index layer in the first repetitively laminated structure12-11 and the higher refractive index layer in the second repetitivelylaminated structure 12-12 may be configured to provide different phasedifferences. Alternatively, the lower refractive index layer in thefirst repetitively laminated structure 12-11 and the lower refractiveindex layer in the second repetitively laminated structure 12-12 may beconfigured to provide different phase differences. In this case, thelower refractive index layer in the first repetitively laminatedstructure 12-11 and the lower refractive index layer in the secondrepetitively laminated structure 12-12 may provide the same phasedifference, or the higher refractive index layer in the firstrepetitively laminated structure 12-11 and the higher refractive indexlayer in the second repetitively laminated structure 12-12 may providethe same phase difference.

That is, since at least one of the phase differences between two layersin the first repetitively laminated structure 12-11 and the phasedifference between two layers in the second repetitively laminatedstructure 12-12 is different, the first repetitively laminated structure12-11 and the second repetitively laminated structure 12-12 may havedifferent optical characteristics.

It is noted that any suitable method may be utilized to differently format least one of the phase differences between two layers in the firstrepetitively laminated structure 12-11 and the phase differences betweentwo layers in the second repetitively laminated structure 12-12. Thatis, the phase differences may be different from each other by usingdifferent materials configuring the corresponding layers, or thematerials configuring the corresponding layer are the same as eachother, but the phase differences may be differently provided accordingto different thicknesses of the layers. Further, the phase differencesmay be differently set by changing a component ratio of the materialconfiguring the corresponding layers.

As seen in FIG. 8, the higher refractive index layer and the lowerrefractive index layer may be formed by the same polymer, but havedifferent phase differences by differently forming the thicknesses ofthe corresponding layers.

FIG. 8 is a cross-sectional view of a reflective polarizer, according toexemplary embodiments.

As seen in FIG. 8, the lower polarizer 12 is a reflective polarizer, andincludes two first repetitively laminated structures 12-11, one secondrepetitively laminated structure 12-12, and a plurality of buffer layers12-5 disposed therebetween, as well as disposed on the outermostsurfaces of the lower polarizer.

In the first repetitively laminated structure 12-11 and the secondrepetitively laminated structure 12-12, two layers having differentrefractive indices may be repetitively formed upon one another. Thefirst repetitively laminated structure 12-11 and the second repetitivelylaminated structure 12-12 have different optical characteristics. Tothis end, phase differences of at least one corresponding layerconfiguring the first repetitively laminated structure 12-11 and thesecond repetitively laminated structure 12-12 may be different from eachother.

That is, the first repetitively laminated structure 12-11 and the secondrepetitively laminated structure 12-12 may not be formed by differentmaterials. In other words, the first repetitively laminated structure12-11 and the second repetitively laminated structure 12-12 may beformed using polymer A as the first refractive index layer and polymer Bas the second refractive index layer. However, as illustrated in FIG. 8,the second refractive index layer (i.e., polymer B) may be thicker thanthe first refractive index layer (i.e., polymer A) in the firstrepetitively laminated structure 12-11. In the second repetitivelylaminated structure 12-12, however, the second refractive index layer(i.e., polymer B) and the first refractive index layer (i.e., polymer A)may be formed to the same thickness. It is noted, however, that thefirst refractive index layer and the second refractive index layer maybe different from each other in only a refractive index with respect toone axial direction among three axial directions.

As such, since the thickness relationship between the first refractiveindex layer and the second refractive index layer is different, phaseretardations occurring as a result of the configuration of the layersare different from each other, and accordingly, optical characteristicsare different from each other.

It is also noted that, as seen in FIG. 8, the number of total layersincluded in the first repetitively laminated structure 12-11 and thesecond repetitively laminated structure 12-12 is the same, and the totalthicknesses are the same as each other. However, according to exemplaryembodiments, the total number of layers (e.g., 275 layers) may bedifferent from each other, and the total thicknesses may be differentfrom each other.

According to exemplary embodiments, two first repetitively laminatedstructures 12-11 may be disposed at the lower portion of lower polarizer12, and one second repetitively laminated structure 12-12 may bedisposed at an upper portion of the lower polarizer 12. Here, the firstrepetitively laminated structure 12-11 has a reflective polarizationcharacteristic. That is, a partial polarization of light supplied fromthe backlight unit 500 may be reflected, and the rest of the light maybe transmitted. The second repetitively laminated structure 12-12,however, may include a reflective polarization characteristic, but mayinclude a compensation film characteristic. That is, light passingthrough the two first repetitively laminated structures 12-11 at thelower portion of lower polarizer 12 may be light of a predeterminedpolarization component. When the light is incident on the secondrepetitively laminated structure 12-12, since the light meets with amultilayered structure having a different refractive index than thefirst repetitively laminated structure 12-11, an additional phaseretardation may result and have the same effect as the compensationfilm. Therefore, the first repetitively laminated structure 12-11 may beformed with one layer, but may be formed with two or more layers inorder to improve the reflective polarization characteristics. Further,the first repetitively laminated structure 12-11 may be continuouslyformed at a side where the light from the backlight unit 500 is madeincident. Since the light incident to the second repetitively laminatedstructure 12-12 may serve to provide an additional phase difference(phase retardation) as compared with the reflective polarization, onesecond repetitively laminated structure 12-12 may be formed and disposedcloser to the liquid crystal layer 3 than the first repetitivelylaminated structures 12-11. According to exemplary embodiments, in orderto provide sufficient phase retardation, two or more second repetitivelylaminated structures 12-12 may be formed at the upper portion of thelower polarizer 12.

According to exemplary embodiments, a plurality of buffer layers 12-5may be respectively disposed between adjacent repetitively laminatedstructures 12-11 and/or 12-12, as well as disposed on the outermostsurfaces of the outermost repetitively laminated structures 12-11 and12-12. The plurality of buffer layers 12-5 may be formed from one layer(e.g., polymer B having the lower refractive index) among the variouslayers included in the repetitively laminated structures 12-11 and12-12. Each buffer layer 12-5 may be configured to protect or connectthe repetitively laminated structures 12-11 and 12-12.

Referring back to FIG. 1, the lower polarizer 12 is coupled to the outerside of the lower insulation substrate 110, and may include an adhesive12-3 for attachment.

Although not illustrated, a thin film transistor and a pixel electrodemay be disposed on an inner side of the lower insulation substrate 110.The thin film transistor and the pixel electrode may be formed in anyone of various structures. An alignment layer (not shown) may be formedon the pixel electrode.

Hereinafter, the upper panel 200 will be described.

According to exemplary embodiments, the upper polarizer 22 may bedisposed on an upper insulation substrate 210 made of, for instance,transparent glass or plastic.

The upper polarizer 22 may include a structure as illustrated in FIG. 4and may be an absorptive polarizer. That is, the upper polarizer 22,which is an absorptive polarizer, may include a TAC layer 22-2 disposedon the upper surface of a PVA layer 22-1, and a biaxial compensationlayer 22-3 may be disposed positioned on the lower surface of the PVAlayer 22-1. The biaxial compensation layer 22-3 is configured to providephase retardation to improve display quality.

According to exemplary embodiments, the upper polarizer 22 may becoupled to an outer side of the upper insulation substrate 210. An outersurface of the TAC layer 22-2 of the upper polarizer 22 may be subjectedto one or more surface treatments, such as one or more anti-glare oranti-reflection treatments.

While not illustrated, a light blocking member, a color filter, and acommon electrode may be disposed on (or formed inside) the upperinsulation substrate 210. According to exemplary embodiments, at leastone of the light blocking member, the color filter, and the commonelectrode may be formed inside the lower insulation substrate 110. Analignment layer (not shown) may be disposed below the common electrode.

A liquid crystal layer 3 may be disposed between the upper panel 200 andthe lower panel 100.

The liquid crystal layer 3 may have negative dielectric anisotropy andmay include liquid crystal molecules that, in a vertically aligned mode,have long axes vertical to the surfaces of panels 100 and 200 when anelectric field is not applied, and which are aligned in a verticaldirection to the electric field when the electric field is applied bythe pixel electrode and the common electrode. Additionally oralternatively, the liquid crystal molecules may be of an in-planeswitching (IPS) type and/or of a plane to line switching (PLS) type thathave their long axes horizontal to the surfaces of panels 100 and 200when an electric field is not applied to the liquid crystal layer 3, andthat rotate in a horizontal surface according to a horizontal electricfield applied by the pixel electrode and the common electrode.

As such, a liquid crystal display according to exemplary embodiments mayinclude a lower polarizer 12 that is formed as a reflective polarizerand at least two repetitively laminated structures having differentoptical characteristics in the lower polarizer 12. As a result, aninterference colors typically caused at a side of a display panel thatare generated when only the repetitively laminated structures having thesame optical characteristic are used in the lower polarizer 12 may beavoided.

The above-noted interference colors and avoidance thereof is describedin more detail in association with FIGS. 9-12.

FIGS. 9-12 are diagrams of display characteristics of a liquid crystaldisplay, according to exemplary embodiments.

FIG. 9 provides display characteristics associated with a liquid crystaldisplay utilizing a CCFL as a light source, which are illustrated in thefirst row, and display characteristics associated with a liquid crystaldisplay utilizing a LED as the light source, which are illustrated inthe second row. Further, Comparative Examples in which only therepetitively laminated structures having the same optical characteristicare used in the lower polarizer 12 are illustrated in a left column, andthe Examples in which at least two repetitively laminated structureshaving different optical characteristics are used according to exemplaryembodiments are illustrated in a right column. It is noted that theliquid crystal display associated with the right column results wasconfigured as described in association with FIG. 8.

In the case of using the CCFL as the light source, it was verified thata lot of interference colors were generated as compared with the case ofusing the LED as the light source. It was also verified that when atleast two repetitively laminated structures having different opticalcharacteristics are used in the lower polarizer 12, the interferencecolors were prevented.

In FIGS. 10 and 11, in the case of the Comparative Examples and theExamples according to exemplary embodiments associated with FIG. 8,front white luminance (front Lw), a front CR, side white luminance (sideLw), and a side CR are compared with each other, and FIG. 10 illustratesthe case of using the LED as the light source, and FIG. 11 illustratesthe case of using the CCFL as the light source.

As can be seen in comparing FIGS. 10 and 11, the liquid crystal displaysaccording to exemplary embodiments associated with FIG. 8, the side orfront CR was slightly decreased as compared with the ComparativeExamples, but the decrease was not substantial enough to cause anoticeable problem for users. Accordingly, when at least tworepetitively laminated structures having different opticalcharacteristics were used in the lower polarizer 12, display quality wasnot deteriorated.

In FIG. 12, unlike the exemplary embodiments associated with FIG. 8(i.e., the left drawing associated with the Comparative Example) andFIG. 8, a characteristic according to viewing angles of the exemplaryembodiments associated with FIG. 8 (i.e., the right drawing) in whichall of the three repetitively laminated structures of the lowerpolarizer 12 are formed as the repetitively laminated structure 12-12 isillustrated. In this case, the light source used the CCFL. The CCFL waschosen for demonstration because it typically is associated with largeinterference color problems.

As illustrated in FIG. 12, the display characteristics of the two casesare almost similar to each other, but in the right drawing, portionswhere the interference colors are clearly shown exist at 90 degrees and270 degrees. It was verified that when three second repetitivelylaminated structures 12-12 were formed, a portion that supplied thephase difference did not exist like the compensation film, and as aresult, it was difficult to reduce the interference colors. Further, itwas verified that the portion that supplied the phase difference was alayer that was closest to the liquid crystal layer 3.

Hereinafter, interference colors according to thicknesses (or componentratios) of the first refractive index layer and the second refractiveindex layer will be described with reference to FIGS. 13 and 14.

FIGS. 13 and 14 are diagrams of display characteristics of a liquidcrystal display, according to exemplary embodiments.

FIG. 13 illustrates a case of using a CCFL as a light source. Thedrawing positioned at the leftmost side of the first row illustrates aComparative Example in which three first repetitively laminatedstructures 12-11 are disposed in the lower polarizer 12, and the firstrepetitively laminated structure 12-11 is a case where a thickness ratio(or component ratio) between the first refractive index layer and thesecond refractive index layer is 65:101. Even in other Examples of FIG.13, the thickness ratio (or component ratio) of the first repetitivelylaminated structure 12-11 is the same as above.

The other drawings of FIG. 13 are drawings in which the secondrepetitively laminated structure 12-12 is included as associated withthe exemplary embodiments of FIG. 8, and the display characteristics aredescribed while changing the thickness ratio (or component ratio)between the first refractive index layer and the second refractive indexlayer.

The drawing of the second column of the first row illustrates that thethickness ratio (or component ratio) between the first refractive indexlayer and the second refractive index layer in the second repetitivelylaminated structure 12-12 is 70:96, the drawing of the third column ofthe first row illustrates that the thickness ratio (or component ratio)between the first refractive index layer and the second refractive indexlayer in the second repetitively laminated structure 12-12 is 83:83, andthe drawing of the fourth column of the first row illustrates that thethickness ratio (or component ratio) between the first refractive indexlayer and the second refractive index layer in the second repetitivelylaminated structure 12-12 is 90:76. The drawing of the first column ofthe second row illustrates that the thickness ratio (or component ratio)between the first refractive index layer and the second refractive indexlayer in the second repetitively laminated structure 12-12 is 100:66,the drawing of the second column of the second row illustrates that thethickness ratio (or component ratio) between the first refractive indexlayer and the second refractive index layer in the second repetitivelylaminated structure 12-12 is 110:56, the drawing of the third column ofthe second row illustrates that the thickness ratio (or component ratio)between the first refractive index layer and the second refractive indexlayer in the second repetitively laminated structure 12-12 is 120:46,and the drawing of the fourth column of the second row illustrates thatthe thickness ratio (or component ratio) between the first refractiveindex layer and the second refractive index layer in the secondrepetitively laminated structure 12-12 is 150:16.

As illustrated in FIG. 13, it was verified that all the interferencecolors were improved in other drawings as compared with the ComparativeExample disposed at the first column of the first row. Since a value ofthe thickness (or component ratio) of the first refractive index layerdivided by the thickness (or component ratio) of the second refractiveindex layer is 0.6435, a value of the thickness (or component ratio) ofthe first refractive index layer divided by the thickness (or componentratio) of the second refractive index layer (hereinafter, simplyreferred to as a thickness ratio or component ratio) in the secondrepetitively laminated structure 12-12 is 0.644 or more, and in someexemplary embodiments, may be more than 1. In the case of the fourthcolumn of the second row in FIG. 13, the value may be more than 9.375.

In FIG. 13, the case of the most improved interference color is the caseof the third column and the fourth column of the first row, and in thiscase, the range of the thickness ratio or the component ratio may be 1to 1.184.

Hereinafter, a case where the light source is an LED will be describedwith reference to FIG. 14.

The drawing positioned at the leftmost side of the first row illustratesthe Comparative Example in which three first repetitively laminatedstructures 12-11 are positioned in the lower polarizer 12, and the firstrepetitively laminated structure 12-11 is a case where a thickness ratio(or component ratio) between the first refractive index layer and thesecond refractive index layer is 65:101. In the other Examples of FIG.14, the thickness ratio (or component ratio) of the first repetitivelylaminated structure 12-11 is the same as above.

The other drawings of FIG. 14 are drawings in which the secondrepetitively laminated structure 12-12 is included as associated withthe exemplary embodiments of FIG. 8, and the display characteristics aredescribed while changing the thickness ratio (or component ratio)between the first refractive index layer and the second refractive indexlayer.

The drawing of the second column of the first row illustrates that thethickness ratio (or component ratio) between the first refractive indexlayer and the second refractive index layer in the second repetitivelylaminated structure 12-12 is 70:96, the drawing of the third column ofthe first row illustrates that the thickness ratio (or component ratio)between the first refractive index layer and the second refractive indexlayer in the second repetitively laminated structure 12-12 is 83:83, andthe drawing of the fourth column of the first row illustrates that thethickness ratio (or component ratio) between the first refractive indexlayer and the second refractive index layer in the second repetitivelylaminated structure 12-12 is 90:76. The drawing of the first column ofthe second row illustrates that the thickness ratio (or component ratio)between the first refractive index layer and the second refractive indexlayer in the second repetitively laminated structure 12-12 is 100:66,the drawing of the second column of the second row illustrates that thethickness ratio (or component ratio) between the first refractive indexlayer and the second refractive index layer in the second repetitivelylaminated structure 12-12 is 110:56, the drawing of the third column ofthe second row illustrates that the thickness ratio (or component ratio)between the first refractive index layer and the second refractive indexlayer in the second repetitively laminated structure 12-12 is 120:46,and the drawing of the fourth column of the second row illustrates thatthe thickness ratio (or component ratio) between the first refractiveindex layer and the second refractive index layer in the secondrepetitively laminated structure 12-12 is 150:16.

As illustrated in FIG. 14, it was verified that all the interferencecolors were improved in the other drawings as compared with theComparative Example disposed at the first column of the first row. Sincea value of the thickness (or component ratio) of the first refractiveindex layer divided by the thickness (or component ratio) of the secondrefractive index layer is 0.6435, a value of the thickness (or componentratio) of the first refractive index layer divided by the thickness (orcomponent ratio) of the second refractive index layer (hereinafter,simply referred to as a thickness ratio or component ratio) in thesecond repetitively laminated structure 12-12 is 0.644 or more, and insome exemplary embodiments, may be more than 1. In the case of thefourth column of the second row in FIG. 14, the value may be more than9.375.

In FIG. 14, the most improved interference color is the case of thethird column and the fourth column of the first row, and in this case,the range of the thickness ratio or the component ratio may be 1 to1.184.

Referring to FIGS. 13 and 14, in the first repetitively laminatedstructure 12-11 and the second repetitively laminated structure 12-12,the thicknesses of the first refractive index layer and the secondrefractive index layer may be reversed. That is, in the ComparativeExamples of FIGS. 13 and 14, the thickness of the second refractiveindex layer is increased in the first repetitively laminated structure12-11, but in the other Examples, the thickness of the second refractiveindex layer is decreased in the second repetitively laminated structure12-12.

In FIGS. 13 and 14, in a state where the combined thickness of the firstrefractive index layer and the second refractive index layer is set tobe constant, an experiment was performed while changing the thicknessratio/component ratio. However, the combined thickness of the firstrefractive index layer and the second refractive index layer may bedifferent in the first repetitively laminated structure 12-11 and thesecond repetitively laminated structure 12-12, and the entire thicknessof the first repetitively laminated structures 12-11 may be differentfrom the entire thickness of the second repetitively laminatedstructures 12-12.

FIG. 15 is a diagram of a manufacturing method of the reflectivepolarizer of FIG. 8, according to exemplary embodiments.

First, two first repetitively laminated structures 12-11 where the firstrefractive index layer and the second refractive index layer arerepetitively laminated and the buffer layer 12-5 disposed between andoutside the first repetitively laminated structures 12-11 aresequentially laminated according to a thickness ratio (or componentratio) of the first repetitively laminated structures 12-11, as can beseen in FIG. 15A.

Further, as illustrated at the top of FIG. 15A, the second repetitivelylaminated structure 12-12 where the first refractive index layer and thesecond refractive index layer are repetitively laminated and the bufferlayer 12-5 is disposed at one side of the second repetitively laminatedstructure are sequentially laminated according to a thickness ratio (orcomponent ratio) of the second repetitively laminated structures 12-12.

Thereafter, as illustrated in FIG. 15B, the portion including the secondrepetitively laminated structure 12-12 is laminated at the upper side ofthe portion including the first repetitively laminated structure 12-11.

Thereafter, as illustrated in FIG. 15C, the lower polarizer 12 iscompleted by stretching the structure in one direction.

While the stretching method has been described, it is noted thatexemplary embodiments are not so limited and any other suitable methodto elongate the resultant structure may be utilized, which may includeforming the resultant structure in the desired dimensions.

It is noted that the exemplary embodiments may be modified in variousmanners, some of which will be described in association with FIGS. 16and 17.

FIG. 16 is a cross-sectional view of a reflective polarizer, accordingto exemplary embodiments.

As seen in FIG. 16, only one first repetitively laminated structure12-11 is used unlike as illustrated in FIG. 8. As a result, the numberof buffer layers 12-5 is reduced as compared with the illustration ofFIG. 8.

Although only one first repetitively laminated structure 12-11 is used,the exemplary embodiment of FIG. 16 may be applied to a liquid crystaldisplay, which may be used in the case where a reflective polarizationcharacteristic is good, or may be used in the case where the reflectivepolarization characteristic is bad.

According to exemplary embodiments, the number of total layers in thefirst repetitively laminated structure 12-11 of FIG. 16 may be differentform the number of total layers of the first repetitively laminatedstructure 12-11 as illustrated in FIG. 8. In exemplary embodiments, morelayers may be included in the exemplary embodiments of FIG. 16.

FIG. 17 is a cross-sectional view of a liquid crystal display, accordingto exemplary embodiments. FIG. 18 is a diagram of displaycharacteristics of the liquid crystal display of FIG. 17, according toexemplary embodiments.

According to exemplary embodiments, the lower polarizer 12 may besimilarly configured as described in FIG. 8.

However, according to exemplary embodiments, the upper polarizer 22 maybe modified, and will be described with reference to FIG. 17.

In general, the liquid crystal display of FIG. 17 is similar to as theliquid crystal display described in association with FIG. 1. However, inFIG. 17, the liquid crystal layer 3 and the upper and lower polarizers22′ and 12′ are illustrated.

The liquid crystal display includes backlight unit 500, optical sheet25, lower panel 100, liquid crystal layer 3, and upper panel 200.

While not illustrated, the backlight unit 500 includes a light source, alight guide plate, and a reflector. The optical sheet 25 is disposed onthe backlight unit 500.

The configuration of backlight unit 500 enables light supplied from thelight source to pass through the light guide plate and the reflector,and thereby, to be discharged upward from the backlight unit 500 andpass through the optical sheet 25 disposed on the backlight unit 500. Inthis manner, the light may propagate through lower panel 100, liquidcrystal layer 3, and upper panel 200.

According to exemplary embodiments, the light source may be (orotherwise include), for example, a fluorescent lamp (such as a CCFL), aLED, and/or the like. The light source may be disposed on a side or alower surface of the backlight unit 500.

The optical sheet 25 may include at least one optical sheet and mayinclude a prism sheet including a prism structure or a diffusion film,such as a diffuser. In exemplary embodiments, the optical sheet 25 maynot include a luminance improvement film that typically includes twolayers having different refractive indices that are repetitively formed.Namely, because a lower polarizer 12 may be utilized that includes arepetitively laminated structure 12-11 that includes a multilayer (e.g.,two layer) structure having different refractive indices repetitivelyformed, improved characteristics in luminance may be achieved withoutthe use of a luminance improvement film associated with optical sheet25.

Lower panel 100, liquid crystal layer 3, and upper panel 200 aredisposed on the backlight unit 500 and optical sheet 25.

First, the lower panel 100 will be described.

A lower polarizer 12′ is coupled below a lower insulation substrate 110,which may be made of transparent glass or plastic.

The lower polarizer 12′ may be a reflective polarizer, and may includeonly the first repetitively laminated structure 12-11 unlike exemplaryembodiments described in association with FIG. 8. While not illustrated,the lower polarizer 12′ may also include a buffer layer 12-5 accordingto exemplary embodiments. The lower polarizer 12′ may also include aplurality of first repetitively laminated structures 12-11.

The buffer layer 12-5 may be configured to protect or connect the firstrepetitively laminated structures 12-11.

The lower polarizer 12′ is coupled to the outer side of the lowerinsulation substrate 110, and includes an adhesive (not illustrated) forattachment.

Although not illustrated, a thin film transistor and a pixel electrodemay be disposed on an inner side of the lower insulation substrate 110.The thin film transistor and the pixel electrode may be formed in anyone of various structures. An alignment layer (not shown) may bedisposed on the pixel electrode.

Hereinafter, the upper panel 200 will be described.

An upper polarizer 22′ is disposed on an upper insulation substrate 210made of transparent glass or plastic.

The upper polarizer 22′ includes a C plate 22-4 unlike FIG. 7, as anabsorptive polarizer.

That is, referring to FIG. 17, in the upper polarizer 22,′ which is anabsorptive polarizer, a TAC layer 22-2 is disposed on the upper surfaceof a PVA layer 22-1, and the C plate 22-4, which is a monoaxialcompensation layer, and a biaxial compensation layer 22-3 are disposedon the lower surface of the PVA layer 22-1. The C plate 22-4 and thebiaxial compensation layer 22-3 may be configured to provide a phaseretardation to improve display quality. According to exemplaryembodiments, one of the C plate 22-4 and the biaxial compensation layer22-3 may be omitted.

The upper polarizer 22′ is coupled to an outer side of the upperinsulation substrate 210. An outer surface of the TAC layer 22-2 of theupper polarizer 22′ may be subjected to one or more surface treatments,such as one or more anti-glare or anti-reflection treatments.

While not illustrated, a light blocking member, a color filter, and acommon electrode may be disposed on or inside the upper insulationsubstrate 210. According to exemplary embodiments, at least one of thelight blocking member, the color filter, and the common electrode may beformed inside the lower insulation substrate 110. An alignment layer(not shown) may be disposed below the common electrode.

A liquid crystal layer 3 may be disposed between the upper panel 200 andthe lower panel 100.

The liquid crystal layer 3 may have negative dielectric anisotropy andmay include liquid crystal molecules of a VA type that have long axesthat are vertical to the surfaces of panels 100 and 200 when an electricfield is not applied to liquid crystal layer 3, and that are aligned ina vertical direction to the electric field when the electric field isapplied by the pixel electrode and the common electrode. Additionally oralternatively, the liquid crystal molecules may be of an IPS type and/ora PLS type that have long axes that are horizontal to the surfaces ofpanels 100 and 200 when an electric field is not applied, and thatrotate in a horizontal surface according to a horizontal electric fieldforming via the pixel electrode and the common electrode.

As such, in the liquid crystal display, the C plate 22-4 is added to theupper polarizer 22′ and only the first repetitively laminated structure12-11 is included in the lower polarizer 12′ unlike as described inassociation with FIG. 8. As a result, a problem that interference colorsare generated is removed by the added C plate 22-4 of the upperpolarizer 22′.

Illustrative display characteristics of the liquid crystal displaydescribed in association with FIG. 17 are described in association withFIG. 18.

In FIG. 18, a case of using a CCFL as a light source is illustrated, andthe left drawing is a Comparative Example, in which the C plate 22-4 isnot added to the upper polarizer and the lower polarizer includes onlythe first repetitively laminated structure. The right drawing isassociated with the liquid crystal display configured as described inassociation with the exemplary embodiments of FIG. 17.

As illustrated in FIG. 18, the interference colors may be reduced in thecase of using the liquid crystal display configured in association withthe exemplary embodiments of FIG. 17. The results associated with theright drawing are the results of a characteristic of the firstrefractive index layer of the first repetitively laminated structureused in exemplary embodiments includes a characteristic of an A plate,and as a result, the characteristics compensate for each other when theC plate is added to the upper polarizer, as described in associationwith FIG. 17.

As described above, in the case of FIGS. 8-18, exemplary embodiments inwhich the interference colors generated when the repetitively laminatedstructures are included in the lower polarizer in the liquid crystal ofthe VA mode or the IPS and PLS mode are reduced were described.

While certain exemplary embodiments and implementations have beendescribed herein, other embodiments and modifications will be apparentfrom this description. Accordingly, the invention is not limited to suchembodiments, but rather to the broader scope of the presented claims andvarious obvious modifications and equivalent arrangements.

What is claimed is:
 1. A polarizer, comprising: a first laminatedstructure comprising a first layer having a first refractive index and asecond layer having a second refractive index, wherein the first andsecond refractive indices are different from each other; a secondlaminated structure disposed on the first laminated structure, thesecond laminated structure comprising a third layer having a thirdrefractive index and a fourth layer having a fourth refractive index,wherein the third and fourth refractive indices are different from eachother; and a buffer layer disposed between the first laminated structureand the second laminated structure.
 2. The polarizer of claim 1, whereinthe first refractive index is substantially the same as the thirdrefractive index.
 3. The polarizer of claim 2, wherein the secondrefractive index is substantially the same as the fourth refractiveindex.
 4. The polarizer of claim 3, wherein the first layer and thethird layer comprise a first material, and the second layer and thefourth layer comprise a second material, and wherein a component ratioof the first material of the first layer to the second material of thesecond layer is different from a component ratio of the first materialof the third layer to the second material of the fourth layer.
 5. Thepolarizer of claim 3, wherein a thickness ratio of the first layer tothe second layer is different from a thickness ratio of the third layerto the fourth layer.
 6. The polarizer of claim 5, wherein the firstlayer and the third layer comprise the same material, and the secondlayer and the fourth layer comprise the same material.
 7. The polarizerof claim 1, wherein the first layer and the third layer comprise a firstmaterial, and the second layer and the fourth layer comprise a secondmaterial, and wherein a component ratio of the first material of thefirst layer to the second material of the second layer is different froma component ratio of the first material of the third layer to the secondmaterial of the fourth layer.
 8. The polarizer of claim 1, wherein athickness ratio of the first layer to the second layer is different froma thickness ratio of the third layer to the fourth layer.
 9. Thepolarizer of claim 8, wherein the first layer and the third layercomprise the same material, and the second layer and the fourth layercomprise the same material.
 10. The polarizer of claim 1, wherein thefirst layer and the third layer comprise different material from eachother.
 11. The polarizer of claim 1, wherein the second layer and thefourth layer comprise different material from each other.
 12. A liquidcrystal display, comprising: a first panel comprising: a first polarizerconfigured as an absorptive polarizer, and a first insulation substrate;a second panel comprising: a second polarizer, and a second insulationsubstrate; a liquid crystal layer disposed between the first panel andthe second panel; and a backlight providing unit configured to supplylight, wherein the second panel is disposed on the backlight providingunit, and wherein the second polarizer comprises: a first laminatedstructure comprising a first layer having a first refractive index and asecond layer having a second refractive index, wherein the first andsecond refractive indices are different from each other; a secondlaminated structure disposed on the first laminated structure, thesecond laminated structure comprising a third layer having a thirdrefractive index and a fourth layer having a fourth refractive index,wherein the third and fourth refractive indices are different from eachother; and a buffer layer disposed between the first laminated structureand the second laminated structure.
 13. The polarizer of claim 12,wherein the first refractive index is substantially the same as thethird refractive index.
 14. The polarizer of claim 13, wherein thesecond refractive index is substantially the same as the fourthrefractive index.
 15. The polarizer of claim 14, wherein the first layerand the third layer comprise a first material, and the second layer andthe fourth layer comprise a second material, and wherein a componentratio of the first material of the first layer to the second material ofthe second layer is different from a component ratio of the firstmaterial of the third layer to the second material of the fourth layer.16. The polarizer of claim 14, wherein a thickness ratio of the firstlayer to the second layer is different from a thickness ratio of thethird layer to the fourth layer.
 17. The polarizer of claim 16, whereinthe first layer and the third layer comprise the same material, and thesecond layer and the fourth layer comprise the same material.
 18. Thepolarizer of claim 12, wherein the first layer and the third layercomprise a first material, and the second layer and the fourth layercomprise a second material, and wherein a component ratio of the firstmaterial of the first layer to the second material of the second layeris different from a component ratio of the first material of the thirdlayer to the second material of the fourth layer.
 19. The polarizer ofclaim 12, wherein a thickness ratio of the first layer to the secondlayer is different from a thickness ratio of the third layer to thefourth layer.
 20. The polarizer of claim 19, wherein the first layer andthe third layer comprise the same material, and the second layer and thefourth layer comprise the same material.
 21. The polarizer of claim 12,wherein the first layer and the third layer comprise different materialfrom each other.
 22. The polarizer of claim 12, wherein the second layerand the fourth layer comprise different material from each other.